1. Field of the Invention
The present invention relates to a structure and manufacturing method for lowering the height of a molded coil directly connected face to face to a conductor pattern of a circuit board.
2. Technical Background of the Invention and its Problem
FIG. 8 is a sectional view showing a conventional molded coil. A spiral coil 1 is buried in a synthetic resin body 2 and both end parts 3, 5 of the coil 1 are horizontally exposed as face-to-face connection terminals. Number 4 denotes a through hole to which a threaded core not shown in figures is screwed. A molded coil such as the one mentioned above requires dimensions A, B of the resin body 2 under the coil 1. Though the dimensions are essential for pulling out the end part under the coil 1 (the lower end part 3 as a terminal) from the resin body 2 to a lower side, unlike a spiral part of the coil 1, and do not directly relate to the characteristics of the coil itself.
FIG. 9 is a partially enlarged view showing the lower end part 3 when the coil 1 is molded. Since it is difficult to orthogonally bend a curved part 12 accurately when the spiral part of the coil 1 is bent downwards, if the dimension A is reduced, the curved part 12 will touch an edge 8 of a hole 7 of a metal mold 6 to which the lower end part 3 is inserted and engage with it by the pressure of the injected resin when molded. This frequently results in failure that the molded coil 12 cannot be disengaged from the metal mold 6 after molding.
FIG. 10 is a partially enlarged view showing the molded coil when the lower end part 3 of the molded coil 1 is bent horizontally. The dimension B is required as a space where a flat metal 10 is clamped to bend the lower end part 3 by clamping the flat metal 10 between a bottom face 9 and the lower end part 3 of the molded coil.
The dimensions A, B are, accordingly, essential only for pulling out the lower end part 3 of the coil 1 as the face-to-face connection terminal, and do not directly relate to the characteristics of the coil. It is therefore desirable to reduce them for lowering the height of the molded coil or increasing inductance in same height.